Through-ringing amplifier.



C. S. DEMAREST.

THROUGH RINGING AMPLIFIER.

I 1 APPLICATION FILEDOCT. 16. I917. 1,280,969. Patented Oct. 8,1918.

2 SHEETS-SHEET l.

@iA MHIII- IN V EN TOR. C. @flemamsl ATTORNEY ED STATES PATE OFFICE.

CHARLES S. DEMABEST, OF FLATBUSH, NEW YORK, ASSIGNOR TO AMERICAN TELE- PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

THROUGH BDTGING AMPLIFIER.

Specification of Letters Patent.

Patented Oct. 8, 1918.

Application filed October 16, 1917. Serial No. 196,895.

To all 2071 om it may concern:

Be it known that I CHARLES S. DEM- AREST, residing at Flatbush, in the county of Kings and State of New York, have invented certain Improvements in Through- Ringing Amplifiers, of which the following is a specification.

This invention relates to ringing equipment for use on transmission lines and also for use on transmission lines including repeater elements.

It is one of the objects of the invention to provide a means for amplifying ringing current in a transmission line without affecting the balance of the repeaters included therein, or interfering with the transmision. Another object of the invention is to increase the ringing range on long toll lines not equipped with telephone repeaters. A further object is to obviate the tendency for false ringing which is prevalent in former types of .through line repeater equipment. Other and further objects of the invention will be clear from the detailed description to be given later.

In former types of through line repeaters many difiiculties have been experienced in through ringing due to the occurrence of electrical and mechanical interference with the relays and interrupters mociated with the apparatus and false ringing often results from such interference. For the purpose of eliminating the relays and interrupters from the through line repeater equipment and "at the same time providing satisfactory means for through ringing, the apparatus embodied in this invention has been provided. Such apparatus includes an intermediate repeater circuit designed to be especially efiicient for amplifying ringing current. When the transmission line includes repeater elements, this intermediate repeater circuit is associated therewith by means of conductors bridged from the midpoints of the input windings of thethrough line repeaters included in the line. When the intermediate repeater circuit is to be used with a transmission line which does not include repeater elements the conductors associating it therewith are bridged directly across the two sections of the transmission line, said sections being interconnected by an artificial line. In order that the transmission of talking currents over the line may not be affected by this intermediate repeater circuit, there is inserted in the conductors designed as to be resonant to currents having a frequency suitable for ringing purposes, such for example as 133 cycles, while at the same time offering a high impedance to currents of talking frequencies. By the above arrangements it will be possible to send amplified ringing current out over a transmision line without interfering with either the transmission or amplification of voice currents thereover, and without the occurrence of false ringing.

The arrangements of the invention may now be more fully understood from the following description taken in connection with the accompanying drawing in the Figures 1 and 2 of which are illustrated the preferred form of the circuit arrangements of the invention: In Fig. 2 the intermediate repeater circuit is shown associated with a transmission line, while in Fig. 1 the intermediate repeater circuit is shown associated with a transmission line which includes the usual type of two way two element repeater. In the Fig. 1 the incoming and outgoing sections of a transmission line are shown at L or L Inserted in the transmission line is the usual type of through line repeater consisting of two amplifiers A and A having their output circuits coupled to the lines L and L respectively by means of the windings 1. 2, and 3, and 4, 5, and 6, and having their input circuits coupled to the lines L and L by means of the transformers 30 and 31 respectively. The transformers 30 and 31 are designed to be especially eflicient for the transmission of voice currents but offer a fairly high impedance to currents of ringing frequency and hence reduce the transmission of ringing currents through the repeater. Inserted in the input circuits of the amplifiers A and A are the potentiometers 32 and 33 for the purpose of regulating the amplification to produce an amplitude desirable for voice currents. As the amplification desirable for voice currents may in practice be considerably lower than the amplification desirable for ringing current, it will be seen that any ringing current, which is transmitted through the transformers 30 and 31 and the potentiometers 32 and 33, arrives at the amplifiers A and A so attenuated that it will not be transmitted out over the lines L or L with the amplitude desirable for practical use, and it is for the purpose of obviating this difliculty that the arrangements to be described later have been provided- F or the sake of convenience. the

known arrangement such as'the mechanical repeater may be used. Associated with the V amplifiers A and A are the artificial lines N and N adapted to simulate the respective sections L and. L of tlie transmission line.

.Bridged from the mid-points of the repeater input windings 5 and 6 arethe conductors 20 and 21 leading to the artificial line N which includes the retardation coils lb and L and the condensers C and C Bridged from the mid-points of the repeater input windings 2 and 3 are the conductors 22 and 23 leading to the artificial line N similar to N and including the retardation coils L and L and the condensers C and C The artificial lines N and N are designed to be resonant to currents of a frequency suitable for ringing, as for example 133 cycles, while ofi'ering a high impedance to currents of talking frequencies. Accordingly the artificial lines N and N prevent talking cur rents from entering and being transmitted over the intermediate repeater circuit but readily allow ringing currents to be transmitted thereover. Furthermore artificial lines N and N tend to balance lines L and L with respect to the intermediate repeater A The artificial lines N and N are interconnected by means of the conductors 13 and 14 in which are'inserted the windings l2 and 16, the neutral points ofwhich are interconnected by th winding 9. In inductive relation to thewinding 9 is the winding 15 which serves as the input winding of the intermediate repeater circuit, said input circuit being completed by the potentiometer 40 and the conductors leading to the grid and filament of amplifier A The potentiometer 40 is ad justed to regulate the amplification of the amplifier A to produce an amplitude desirable for ringing purposes. Associated with the amplifier A 1s an output circuit formed by the conductors 11 and the winding-17, which is in inductive relation to the winding 12. By this inductive relation amplified ringing current may be transmitted to the conductors 13 and 1% and thence over the artificial line N and the conductors 22 and 23 to section L of the transmission line. This amplified ringing current may also be transmitted from the conductors 13 and 14 to section L of the transmission line by way of the artificial line N and the conductors 20 and 21.

In the Fig. 2 the two sections L and L of the transmission line are coupled together by the artificial line N including the retardation-coilslL and L and the condensers C and C instead of a two way through line renaeaeeo peater. This artificial line N is designed to transmit transmission currents efficiently while ofiering a high impedance to ringing currents. Thus the greater part of the ringing currents pass through the intermediate repeater. When such is the case the conductors 20 and 21, and 22 and 23, leading to the artificial lines N and N are connected directly. to the sides of the transmission line and in all other respects the intermediate repeater circuit is similar to that shown in Fig. 1.

- With this description of the apparatus in mind the arrangements of the invention may now be more fully understood from the following description of its operation.

The ringing current coming in over the line L, Fig. 1, will be'transmitted from the mid-points of the windings 5 and 6 and over the conductors 20 and 21 to the artificial line N As has been formerly pointed out this artificial line is so constructed that it ofi ers a high impedance to currents of talkingfrequencies, while being resonant to current having a tre uency suitable for ringing such for examp e as 133 cycles. Accordingly any. talking currents which are transmitted over the conductors 20 and 21 will be practically extinguished by the artificial line N while ringing current will be readily transmitted thereoverl The ringing current will then be transmitted over conductors 13 and 14: and through the winding 9. An induced ringing current will then be set 11 in the winding 15 and will be transmitte to the potentiometer 40 and over the conductors leading to the grid and filament of the amplifier A The ringing current is accordingly amplified by the amplifier A and is transmitted in amplified form out over conductors 11 and through the winding 17. An induced amplified current will then be set up in the windings '12 and 16 and transmitted overv conductors 13 and 14 to the artificial line N As the artificial line N is similar in construction to artificial line N the amplified ringing current will be readily transmitted therethrough, and thence over conductors 22 and 23 to the line L over which it is transmitted in the desired amplified form.

A portion of the amplified ringing current will also be transmitted through the artificial line N and back over the line L but this does not interfere with the operation.

In like manner ringing current coming in over the line L will be transmitted over the conductors 22 and 23 and the artificial line N to the circuit of the amplifier A and thereby be amplified and in turn transmitted out over the line L As the operation is substantially the same for ringing current coming in over the line L, as in the case of ringing current coming in over the line L, no detailed description of the operation is necessary.

aaeopee The operation of the intermediate amplifier circuit illustrated in Fig. 2, when associated with a transmission line which does not include repeater elements, is substantially the same as described above, and the description of its operation will be omitted.

lVhile the invention has been illustrated as embodied in certain specific forms it will be understood that it is capable of embodiment in many and widely varied arrangements without departing from the spiritof the invention.

What is claimed is:

1. In a telephone transmission system, the combination with a transmission line and means included therein for amplifying currents transmitted thereover, said means being adapted to transmit currents of all frequencies within the limits of the frequencies found in the usual voice or telephone currents; of an auxiliary circuit associated with said line for transmitting currents suitable for ringing purposes around said amplifying means, amplifying means included in said auxiliary circuit, and means in said auxiliary circuit between said transmission line and said last mentioned amplifying means for attenuating and practically extinguishing currents suitable for talking purposes.

2. In a telephone transmission system, the combination with a transmission line including a through line repeater and transformer windings located in each side of said line and on each side of said repeater; of an auxiliary circuit bridged from the mid-points of said transformer windings, said auxiliary circuit including means adapted to amplify current suitable for ringing purposes and means between the transmission line and said last mentioned amplifying means for attenuating and practically extinguishing currents suitable for talking purposes.

3. In a telephone transmission system, the combination with a through line repeater adapted to transmit currents of all frequencies within the limits of the frequencies found in the usual voice or telephone currents; of an intermediate amplifying set bridged around said repeater, artificial lines inserted between said intermediate set and said repeater, said artificial lines being so poses, and means in said bridged circuit for attenuating and practically extinguishing currents suitable for talking purposes entering therein.

5. In a signaling system, the combination with a transmission line adapted to transmit currents of all frequencies within the limits of the frequencies found in the usual voice or telephone currents; of an auxiliary circuit shunted around a portion of said transmission line, amplifying means included in said auxiliary circuit, and means in said auxiliary circuit between said amplifying 1 means and said transmission line for attenuating and practically extinguishing currents of certain frequencies.

6. In a signaling system, the combination with a telephone transmission line adapted to transmit currents of all frequencies within the limits of the frequencies found in the usual voice or telephone currents; of an auxiliary circuit shunted around a portion of said transmission line, amplifying means included in said auxiliary circuit adapted to amplify current suitable 'for ringing purposes, and means included therein between said amplifying means and said transmission line for attenuating and practically extinguishing currents suitable for talking purposes.

In testimony whereof, I have signed my nameto this .specification in the presence of two subscribing witnesses, this tenth day of October 191 7.

CHARLES S. DEMAREST.

Witnesses MAY QUINN, ALFRED KAUFMANN. 

